Conventionally, a pusher open rotor is especially constituted of two propellers, each comprising a retaining ring equipped with a plurality of blades. As represented in FIG. 1, a propeller 1 is generally formed by a retaining ring 2 (typically in titanium or composite material) comprising a plurality of radial bores 3 uniformly distributed at its periphery. Each radial bore 3 is adapted to receive a root 4 of a blade 5 equipped with a pivot 6 (also called blade root pivot).
However, a configuration such as described above is likely to present some disadvantages. In fact, propeller 1 constitutes a disk with a relatively high mass that must resist the centrifugal forces applied to it when the propeller shaft rotates. Furthermore, such mass is increased by the metal blade roots 4. In addition, this high mass generates, for the airplane, high fuel consumption.
To reduce this high mass, it is possible to use blades 5 in which the root 4 is in a composite material. In fact, the utilization of such material enables the mass of the assembly formed by the retaining ring 2 and blades 5 to be reduced.
However, airplanes equipped with a pusher open rotor 7 whose propellers 1 are situated at the rear present a primary stream 9 in which gases that may exceed 500 degrees circulate, this primary stream 9 being situated below and near the blade 5 roots 4 (see FIG. 2). Consequently, roots 4 of blade 5 are subjected to high temperatures.
A disadvantage resides in the fact that composite materials don't resist high temperatures very well and deteriorate rapidly. Therefore, the lifetime of a blade comprising a root in a composite material is limited.